The Mayfair property tycoon Vincent Tchenguiz, who last week found himself among nine men targeted in dawn raids by the Serious Fraud Office, ceded control on Monday of the most controversial part of his real estate empire to administrators and is struggling to hang on to certain other assets.

Four holding companies that sit over Britain's largest residential property maintenance empire have appointed administrators from Zolfo Cooper.

The underlying operating companies, including Peverel Property Management, continue to operate unaffected. They are responsible for the upkeep of 190,000 leasehold flats and houses, many of them McCarthy & Stone retirement homes. Administrators were at pains to stress there was nothing to suggest residents' sink funds or other assets had not been properly ring-fenced.

Tchenguiz and his brother Robert are the target of an SFO inquiry along with a number of former senior executives from failed Icelandic bank Kaupthing, where both brothers had been major borrowers.

Tchenguiz, who denies any wrongdoing, claimed the collapse of Peverel companies was a "direct result" of the SFO investigation. He said Merrill Lynch had made a "sudden" decision to demand repayment of a £124.6m loan, plus about £11.4m interest, within 24 hours of his arrest.

The collapse of Peverel-linked companies is likely to throw a spotlight on to protracted debt renegotiations elsewhere in Vincent Tchenguiz's property empire, which includes several residential complexes on the Thames such as St George Wharf in Vauxhall, Charter Quay in Kingston upon Thames and Putney Wharf Tower.

Last month the Guardian revealed that Merrill Lynch had called a default in relation to the Peverel group holding companies and had in effect assumed control of this web of property management companies.

Four other banks – Deutsche Bank, Lloyds Banking Group, BayernLB and Allied Irish Banks – had also declared defaults of other parts of the sprawling property operations. These banks had provided huge loans that allowed Vincent Tchenguiz to build Britain's largest portfolio of residential freeholds, earning ground rents and other fees from hundreds of thousands of leasehold tenants. Many of the underlying freeholds were part of Tchenguiz's Fairhold stable of companies.

Among the most troubled portion of the surviving empire is thought to be a complex corporate structure that is struggling under loans from Lloyds Banking Group. Court papers from an unrelated case, filed by trustees to Tchenguiz Family Trust, claim "in effect [Lloyds has] assumed control of the underlying portfolio". The papers add that Lloyds is "also charging additional default interest of 1.75%" — something another source close to the bank negotiations has said is not true.

Although the arrival of administrators is a blow for Vincent Tchenguiz, he had in effect lost control of the Peverel empire two years ago after putting up shares in several offshore investment vehicles – purportedly valued at more than £220m – as collateral to support a crumbling loan agreement between his brother and the Icelandic bank Kaupthing.

Despite Vincent Tchenguiz's best efforts to resolve his brother's debt crisis, the Kaupthing loan continued to sink into negative equity and was called in as Kaupthing itself collapsed in October 2008. All collateral backing the bad loan – including shares in the Vincent Tchenguiz-controlled offshore investment vehicles – was later seized by the bank's liquidators. But they soon found a problem with the forfeited shares in the British Virgin Islands-based vehicles. The vast majority of assets within an underlying complex web of companies were already pledged to other banks through long-term senior loan agreements.

Moreover, these agreements contain so-called "change of control" clauses, which give these banks the right to call in loans if Vincent Tchenguiz fails to keep control of the corporate structure. Receivers appointed by Kaupthing are in possession of shares but have not formally taken control of the underlying businesses. To do so could trigger a chain of defaults, leaving the shares Kaupthing took as security from Vincent Tchenguiz two and a half years ago valueless.

According to the Tchenguiz camp, Kaupthing's decision to appoint joint receivers over several companies' shares has already triggered various events of default. The papers claim Vincent had repeatedly warned Kaupthing liquidators of "the ruinous impact of ... the appointment of receivers ... on Kaupthing's security position".